This invention relates to power supply circuits for gas discharge lamps, and more specifically relates to such a power supply circuit having a power factor in excess of 0.95.
Electronic ballast circuits for gas discharge lamps are well known. Such circuits should have a power factor in excess of 0.95 for more efficient operation and to meet specifications of various organizations and municipalities.
A very inexpensive ballast circuit, manufactured and sold in the Peoples Republic of China, and identified as "Peking Radio Factory #5" employs a rectifier circuit to increase power factor. This circuit uses three diodes in series, having two capacitors each having one terminal connected to respective ones of the opposite end terminals of the string of diodes and their other terminals connected to respective nodes between the center diode and the outer two diodes of the three-diode chain. The outer ends of the diode chain are connected to the positive and negative output terminals to the lamp circuit. With this connection, the two capacitors will charge in series and discharge in parallel.
The power factor of this prior art circuit was measured to be 0.935. Thus, the circuit is not useful for the numerous applications requiring a power factor in excess of 0.95.